1. Field of the Invention
The present invention relates to an optical fiber gyroscope having a fiber coil which is formed, for example, by winding an optical fiber having a length of several tens meters to several hundreds meters in a predetermined number of turns.
2. Description of the Related Art
Recently, for example, a system has been suggested and practically used, in which a gyroscope is used for a navigation system of an automobile to detect the compass direction. Especially, an optical fiber gyroscope has been suggested, which is extremely advantageous in operability, convenient handling performance, and realization of a compact and light weight system, and which is also advantageous in improvement in durability because there is no mechanically movable component. Development is being rapidly advanced at present in order to practically use such an optical fiber gyroscope.
The system of the optical fiber gyroscope will now be briefly explained. The optical fiber gyroscope is a sensor for detecting the angular velocity based on the phase difference (Sagnac phase difference) between two light beams transmitted in both directions in a fiber coil obtained by winding an optical fiber having a length of several tens meters to several hundreds meters in a predetermined number of turns. The optical fiber gyroscope is classified into those belonging to the open loop system and those belonging to the closed loop system depending on the method for detecting the phase difference.
When it is intended to produce an optical fiber gyroscope which is excellent in, for example, compact and light weight properties and durability as described above, the process for assembling the optical fiber gyroscope especially comprises the steps of winding a lengthy optical fiber around a cylindrical object to produce a fiber coil, optically coupling an optical IC chip (optical waveguide) incorporated with a phase modulator to two ends of the optical fiber led from the fiber coil, optically coupling an optical fiber led from a light source to an optical fiber to be led to a photodetector by using a coupler, optically coupling an optical fiber led from the coupler to the optical IC chip, and packaging the optical IC chip. Therefore, a problem arises in that the operation for assembling the optical fiber gyroscope is extremely complicated.
Especially, when the optical waveguide element (optical IC chip) is connected to the fiber coil, residual lengths after connection are generated at both terminals of the fiber coil. However, in the case of the conventional gyroscope, the fiber coil wound around the reel is fixed to a casing by means of screws or the like. For this reason, a limitation arises concerning the fixed position in the direction of rotation of the reel with respect to the casing, and it is difficult to rewind all of the respective residual lengths of the fiber after connection around the reel in conformity with the respective winding directions. Therefore, it is necessary to separately provide a space for accommodating the residual lengths of the fiber after connection so that the residual lengths of the fiber after connection having been wound in a form of coil are accommodated in the provided space, resulting in an extremely troublesome operation.
Further, the optical fiber, which is led from the coupler, is extremely long as well. Therefore, a problem arises in that the long optical fiber is obstructive during the operation of optical coupling to the optical IC chip. Especially, in order to prevent the optical IC chip from any application of excessive load exerted by the long optical fiber when the optical IC chip is packaged, it is necessary to support the long optical fiber as a bundle, resulting in a problem that the operation efficiency is lowered.
As described above, the conventional optical fiber gyroscope involves the problem that an extremely long period of time is required for the assembling operation, and there is a limit to reduce the production cost.
Further, as described above, the product, which is obtained by connecting the optical IC or the like to the long optical fiber, has been not necessarily satisfactory to exhibit the stable performance as the optical fiber gyroscope, depending on the way of fixation to be used when the product is produced.